Create a Smart relationship - Forest Documentation

What is a Smart Relationship?

Sometimes, you want to create a virtual relationship between two set of data that does not exist in your database. A concrete example could be creating a relationship between two collections available in two different databases. Creating a Smart Relationship allows you to customize with code how your collections are linked together.

Create a BelongsTo Smart Relationship

On the Live Demo example, we have an order which belongsTo a customer which belongsTo a delivery address. We’ve created here a BelongsTo Smart Relationship that acts like a shortcut between the order and the delivery address. A BelongsTo Smart Relationship is created like a Smart Field with the reference option to indicate on which collection the Smart Relationship points to. You will also need to code the logic of the search query.

Rails
Django
Laravel

class Forest::Order
  include ForestLiana::Collection

  collection :Order

  search_delivery_address = lambda do |query, search|

    query.joins(customer: :address).or(Order.joins(customer: :address).where("addresses.country ILIKE ?", "%#{search}%"))

  end

  belongs_to :delivery_address, reference: 'Address.id', search: search_delivery_address do
    object.customer.address
  end
end

Create a HasMany Smart Relationship

On the Live Demo example, we have a product hasMany orders and an order belongsTo customer. We’ve created a Smart Relationship that acts like a shortcut: product hasMany customers. A HasMany Smart Relationship is created like a Smart Field with the reference option to indicates on which collection the Smart Relationship points to.

Rails
Rails
Django
Laravel

class Forest::Product
  include ForestLiana::Collection

  collection :Product

  has_many :buyers, type: ['String'], reference: 'Customer.id'
end

Upon browsing, an API call is triggered when accessing the data of the HasMany relationships in order to fetch them asynchronously. In the following example, the API call is a GET on /Product/:product_id/buyers.We’ve built the right SQL query using Active Record to count and find all customers who bought the current product.Then, you should handle pagination in order to avoid performance issue. The API call has a querystring available which gives you all the necessary parameters you need to enable pagination.Finally, you don’t have to serialize the data yourself. The Forest agent already knows how to serialize your collection (Customer in this example). You can access to the serializer through the serialize_models() function.

Rails.application.routes.draw do
  # MUST be declared before the mount ForestLiana::Engine.
  namespace :forest do
    get '/Product/:product_id/buyers' => 'orders#buyers'
  end

  mount ForestLiana::Engine => '/forest'
end

class Forest::ProductsController < ForestLiana::ApplicationController
  def buyers
    limit = params['page']['size'].to_i
    offset = (params['page']['number'].to_i - 1) * limit

    product = Product.find(params['product_id'])
    customers = Customer.where(order_id: product.orders.ids)

    render json: serialize_models(customers.limit(limit).offset(offset), meta: {count: customers.count})
  end
end

Upon browsing, an API call is triggered when accessing the data of the HasMany relationships in order to fetch them asynchronously. In the following example, the API call is a GET on /app_product/:product_pk/relationships/buyers.

You will have to declare this route in your app urls.py fileThen create the pertained viewWe’ve built the right SQL query using Django ORM to find all customers who bought the current product.Then, you should handle pagination in order to avoid performance issue. The API call has a querystring available which gives you all the necessary parameters you need to enable pagination.Finally, you don’t have to serialize the data yourself. The Forest agent already knows how to serialize your collection (Customer in this example, with the table name app_customer). You can access to the serializer through the Schema().dump function (using marshmallow-jsonapi internally).

Upon browsing, an API call is triggered when accessing the data of the HasMany relationships in order to fetch them asynchronously. In the following example, the API call is a GET on /product/{id}/relationships/buyers.We’ve built the right SQL query using Active Record to count and find all customers who bought the current product.Then, you should handle pagination in order to avoid performance issue. The API call has a querystring available which gives you all the necessary parameters you need to enable pagination.Finally, you don’t have to serialize the data yourself. The Forest agent already knows how to serialize your collection (Customer in this example). You can access to the serializer through the render() function of JsonApi facade.

​What is a Smart Relationship?

​Create a BelongsTo Smart Relationship

​Create a HasMany Smart Relationship

What is a Smart Relationship?

Create a BelongsTo Smart Relationship

Create a HasMany Smart Relationship